In most forms of ransomware, infected computers freeze up and are essentially held hostage until a ransom is paid. One common scheme: False messages claiming to be from the FBI, accusing you of watching child porn or some other illegal online activity. A “fine” is demanded to restore computer function. Chances are that if you pay the money, your computer still won’t be unfrozen. But professional techies using specialized software can usually do the job.

But after infiltrating your computer, the aptly named CryptoLocker ferrets out and encrypts your files – making them unreadable. And fixing encrypted files is a tougher fix.

It gets worse: With CryptoLocker, you’re told, decryption requires a piece of software known as a “private key” – and it’s stored, you’re told, only on the cybercriminals’ server.

You’re instructed (via warnings displayed on your screen) to pay $300 to receive this private key within 100 hours or “the server will destroy the key,” and, in the quaint English of the crooks, “nobody and never will be able to restore files.”

Although anti-virus experts are hard at work, currently there is no fix. So an off-computer backup of files – such as a thumb drive or a remote backup service – is good insurance.